Test method and test arrangement

ABSTRACT

A test method in accordance with one or more embodiments may include: providing a semiconductor device to be tested, the semiconductor device including at least one device cell, the at least one device cell having at least one trench, at least one first terminal electrode region and at least one second terminal electrode region, at least one gate electrode, and at least one additional electrode disposed at least partially in the at least one trench, wherein an electrical potential of the at least one additional electrode may be controlled separately from electrical potentials of the at least one first terminal electrode region, the at least one second terminal electrode region and the at least one gate electrode; and applying at least one electrical test potential to at least the at least one additional electrode to detect defects in the at least one device cell.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of U.S. patent application Ser. No.13/647,480, filed Oct. 9, 2012, which is incorporated herein byreference in its entirety for all purposes.

TECHNICAL FIELD

Various embodiments relate to a test method and a test arrangement.

BACKGROUND

One type of semiconductor devices are trench devices such as trenchtransistors, e.g. trench field effect transistors (FETs) or trenchinsulated-gate bipolar transistors (IGBTs). Trench devices having a highor very high integration density may include a large number (e.g.thousands, tens of thousands, hundreds of thousands, or millions, oreven more) of cells, sometimes also referred to as a cell field. Alreadyone or a few defective cells in a cell field may affect a device'soperating behavior and may even render a device unusable. Thus, it maybe desirable to detect devices with defective cells in a pre-test of thedevices (e.g. in a front end processing stage), for example in order toprevent defective devices from being delivered to customers.

SUMMARY

A test method in accordance with one or more embodiments may include:providing a semiconductor device to be tested, the semiconductor deviceincluding at least one device cell, the at least one device cell havingat least one trench, at least one first terminal electrode region and atleast one second terminal electrode region, at least one gate electrode,and at least one additional electrode disposed at least partially in theat least one trench, wherein an electrical potential of the at least oneadditional electrode may be controlled separately from electricalpotentials of the at least one first terminal electrode region, the atleast one second terminal electrode region and the at least one gateelectrode; and applying at least one electrical test potential to atleast the at least one additional electrode to detect defects in the atleast one device cell.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. The drawings are not necessarilyto scale, emphasis instead generally being placed upon illustrating theprinciples of the invention. In the following description, variousembodiments of the invention are described with reference to thefollowing drawings, in which:

FIG. 1A shows a cross-sectional view of an exemplary semiconductordevice for use with one or more embodiments, and FIG. 1B shows across-sectional view along line A-A′ in FIG. 1A;

FIG. 1C shows a cross-sectional view of a further exemplarysemiconductor device for use with one or more embodiments;

FIGS. 2 to 5 show cross-sectional views of further exemplarysemiconductor devices for use with one or more embodiments;

FIG. 6A shows a diagram illustrating a dependence of a trenchtransistor's breakdown voltage on a number of repetitive avalanchepulses;

FIG. 6B shows a diagram illustrating a dependence of a breakdown voltagefor non-defective transistor cells and defective transistor cells;

FIG. 7A shows a test method according to various embodiments;

FIG. 7B shows a test method according to various embodiments;

FIG. 8 shows a test arrangement according to various embodiments;

FIG. 9 shows a semiconductor device having various cell defects, andfurther shows an electrical scan curve, for illustrating aspects of oneor more embodiments;

FIG. 10 shows a cross-sectional view of an exemplary semiconductordevice for use with one or more embodiments;

FIG. 11 shows a test method according to various embodiments.

DESCRIPTION

The following detailed description refers to the accompanying drawingsthat show, by way of illustration, specific details and embodiments inwhich the invention may be practised. These embodiments are described insufficient detail to enable those skilled in the art to practice theinvention. Other embodiments may be utilized and structural, logical,and electrical changes may be made without departing from the scope ofthe invention. The various embodiments are not necessarily mutuallyexclusive, as some embodiments can be combined with one or more otherembodiments to form new embodiments. Various embodiments are describedin connection with methods and various embodiments are described inconnection with devices. However, it may be understood that embodimentsdescribed in connection with methods may similarly apply to the devices,and vice versa.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration”. Any embodiment or design described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments or designs.

The terms “at least one” and “one or more” may be understood to includeany integer number greater than or equal to one, i.e. one, two, three,four, . . . , etc.

The term “a plurality” may be understood to include any integer numbergreater than or equal to two, i.e. two, three, four, five, . . . , etc.

The word “over”, used herein to describe forming a feature, e.g. a layer“over” a side or surface, may be used to mean that the feature, e.g. thelayer, may be formed “directly on”, e.g. in direct contact with, theimplied side or surface. The word “over”, used herein to describeforming a feature, e.g. a layer “over” a side or surface, may be used tomean that the feature, e.g. the layer, may be formed “indirectly on” theimplied side or surface with one or more additional layers beingarranged between the implied side or surface and the formed layer.

In like manner, the word “cover”, used herein to describe a featuredisposed over another, e.g. a layer “covering” a side or surface, may beused to mean that the feature, e.g. the layer, may be disposed over, andin direct contact with, the implied side or surface. The word “cover”,used herein to describe a feature disposed over another, e.g. a layer“covering” a side or surface, may be used to mean that the feature, e.g.the layer, may be disposed over, and in indirect contact with, theimplied side or surface with one or more additional layers beingarranged between the implied side or surface and the covering layer.

The terms “coupling” or “connection” may be understood to include boththe case of a direct “coupling” or “connection” and the case of anindirect “coupling” or “connection”.

FIG. 1A shows a cross-sectional view of an exemplary semiconductordevice 100 for use with one or more embodiments, and FIG. 1B shows across-sectional view of the semiconductor device 100 along line A-A′ inFIG. 1A.

The semiconductor device 100 may include a first side 123 and a secondside 124, which may be opposite the first side 123. The first side 123may, for example, be a front side of the semiconductor device 100 andthe second side 124 may, for example, be a back side of thesemiconductor device 100. Semiconductor device 100 may be configured asa trench transistor including a plurality of device cells 120 (i.e.transistor cells in this case), each device cell 120 including a trench130. Arrow 121 indicates a trench width w_(t) (width of trench 130), andarrow 122 indicates a distance w_(m) between neighboring trenches 130,sometimes also referred to as mesa width. Three cells 120 are shown forpurposes of illustration, however it may be understood that the numberof cells 120 may be different from three, and may for example be muchlarger than three, e.g. on the order of thousands, tens of thousands, ormillions, or even more, of cells. Semiconductor device 100 may, forexample, be configured as a power transistor, for example as a powerfield-effect transistor. e.g. a power MOSFET.

Semiconductor device 100 may include a semiconductor body 101, in whicha plurality of first terminal electrode regions 102 and a secondterminal electrode region 103 may be formed. The first terminalelectrode regions 102 may be source regions of the transistor, and thesecond terminal electrode region 103 may be a drain region of thetransistor. In this case, the first terminal electrode regions 102 as awhole may also be referred to as a source zone of the transistor, andthe second terminal electrode region 103 may also be referred to as adrain zone of the transistor. The first terminal electrode regions 102may be connected to a first terminal electrode 104 and the secondterminal electrode region 103 may be connected to a second terminalelectrode 105. The first terminal electrode 104 may be a sourceelectrode of the transistor, and the second terminal electrode 105 maybe a drain electrode of the transistor. Alternatively, the firstterminal electrode 104 may be a drain electrode of the transistor, andthe second terminal electrode 105 may be a source electrode of thetransistor. The first terminal electrode 104 may be formed over a firstside 106 of the semiconductor body 101 and the second terminal electrode105 may be formed over a second side 107 of the semiconductor body 101,which may be opposite the first side 106. The first side 106 may, forexample, be a front side of the semiconductor body 101 and the secondside 107 may, for example, be a back side of the semiconductor body 101.The first side 106 of the semiconductor body 101 may, for example, beproximate the first side 123 of the semiconductor device 100 and thesecond side 107 of the semiconductor body 101 may, for example, beproximate the second side 124 of the semiconductor device 100.

The first terminal electrode regions 102 and the second terminalelectrode region 103 may be of the same conductivity type and may, forexample, be n-doped. The second terminal electrode region 103 mayinclude an n-doped (e.g. highly n-doped, e.g. n+ doped) first subregion103 a adjacent to the second terminal electrode 105, and an n-doped(e.g. lightly n-doped, e.g. n-doped) second subregion 103 b adjacent toa side of the first subregion 103 a that faces away from the secondterminal electrode 105. The first subregion 103 a may have a higherdopant concentration than the second subregion 103 b. P-doped bodyregions 108 may be formed between the first terminal electrode regions102 and the second subregion 103 b of the second terminal electroderegion 103. Conductive channels may form in the body regions 108 duringan on-state of the semiconductor device (transistor) 100.

The first terminal electrode regions 102, the body regions 108 and thesecond terminal electrode region 103 may be disposed one over the otherin vertical direction of the semiconductor body 101.

A plurality of first terminal electrode regions 102 may be provided inthe semiconductor body 101, wherein a gate electrode 109 may in eachcase extend from each of the first terminal electrode regions 102through the body regions 108 into the second subregion 103 b of thesecond terminal electrode region 103. The first terminal electroderegions 102 may be connected to a common first electrode 104. The gateelectrodes 109 may be insulated from the semiconductor body 101 by afirst insulating layer 110. The gate electrodes 109 may be connectableor connected to a common potential (e.g. gate driving potential).

An additional electrode 111 may in each case be assigned to each of thegate electrodes 109. The additional electrodes 111 may be locatedentirely within the second subregion 103 b of the second terminalelectrode region 103, with each of the additional electrodes 111 beingsurrounded by a respective second insulating layer 112 and locatedadjacent to a corresponding gate electrode 109. A gate electrode 109 andan additional electrode 111 may in each case be disposed one over theother in a vertical direction of the semiconductor body 101 in a commontrench 130, which may extend in the vertical direction of thesemiconductor body 101 from the first side 106 as far as into the secondterminal electrode region 103. The gate electrodes 109 and additionalelectrodes 111 located in a common trench 130 may be insulated from oneanother by their respective first and second insulating layers 110, 112.

The additional electrodes 111 may be electrically connected together toapply a common electrical potential to all of the additional electrodes111.

As shown in FIG. 1B, the additional electrodes 111 may be configured asplates. A common plate 113 may be provided to apply a common electricalpotential. The common plate 113 may connect the additional electrodes111 with one another and may be insulated from the semiconductor body101 by an electrically insulating layer 114. The electrical connectionof the additional electrodes 111 with one another may be achieved in thetrench (as shown) or may be achieved at the surface of semiconductordevice 100. The gate electrodes 109 may be configured as plates and maybe connected to a common electrical potential via a common plate in asimilar manner as the additional electrodes 111. The electricalconnection of the gate electrodes 109 with one another may be achievedin the trench or may be achieved at the surface of semiconductor device100. It may be provided that there is no electrically conductiveconnection between the gate electrodes 109 and the additional electrodes111. In other words, the gate electrodes 109 and additional electrodes111 may be electrically separated or disconnected from each other.

Each of the gate electrodes 109 and the additional electrodes 111 andeach of the first terminal electrode regions 102 may be part of arespective cell 120 of semiconductor device 100. For example in order tobe able to switch high currents, it may be desirable to provide a largenumber of uniformly configured cells 120.

As all cells 120 of semiconductor device 100 may be connected to thesame electrical potentials (e.g. supply potentials and drivepotentials), all cells 120 may be driven in the same manner. In otherwords, the first terminal electrode regions 102 of all cells 120 may beall connected to the same electrical potential, the gate electrodes 109of all cells 120 may be all connected to the same electrical potential,and the additional electrodes 111 of all cells 120 may be all connectedto the same electrical potential. Furthermore, a common second terminalelectrode region 103 may be provided for all cells 120 according to thisexample.

The gate electrodes 109 may serve to control the switching state of thesemiconductor device (transistor) 100. The additional electrodes 111 mayserve to “shield” the gate electrodes 109 when a supply voltage isapplied between the first and second terminal electrodes 104, 105 (or,between the first terminal electrode regions 102 and the second terminalelectrode region 103), i.e. the additional electrodes 111 may serve toreduce the strength of an electric field acting on the first insulatinglayer 110 of the gate electrodes 109. Thus, the additional electrodes111 may also be referred to as “shield electrodes”. For example in casethat the additional electrodes 111 are configured as plates, they maysometimes also be referred to as field plates.

Due to the aforementioned shielding effect, the first insulating layer110 may, for example, be configured with a smaller thickness whileobtaining the same electric strength as in similar devices withoutadditional (shield) electrodes 111. The reduced insulating layerthickness may, for example, reduce the on-state resistance of thesemiconductor device 100 and/or parasitic capacitances between the gateelectrodes 109 and the second terminal electrode region 103, which maylead to reduced switching losses. Furthermore, as in the semiconductordevice 100 a voltage drop between the first terminal electrode 104 andthe second terminal electrode 105 may occur primarily in the region ofthe additional electrodes 111, it may be possible to increase the dopingof the second terminal electrode region 103 compared to devices havingno additional (shield) electrodes 111, without adding stress in form ofa higher field strength onto the gate electrodes 109.

As mentioned above, the first terminal electrode regions 102 may besource regions and the first terminal electrode 104 may be a sourceelectrode, which may be at the first side 123 of the transistor 100, andthe second terminal electrode region 103 may be a drain region and thesecond terminal electrode 105 may be a drain electrode, which may be atthe second side 124 of the transistor 100. Alternatively, the transistor100 may be implemented in a so-called source down configuration. In thiscase the situation in FIG. 1A may illustratively be flipped so that thesource regions 102 may be at the second side 124 and the drain region103 may be at the first side 123 of the transistor 100. In thisconfiguration, the first terminal electrode 104 may be a drainelectrode, the second terminal electrode 105 may be a source electrode,and the electrodes 109, 111 in the trenches 130 may be connected to padsat the first side 123 of the transistor 100. Alternatively, electrode109 may be connected to a pad at the first side 123 of the transistor100 and electrode 111 may be connected to a pad at the second side 124of the transistor 100. Similar considerations may apply for othersemiconductor devices, e.g. transistors, described herein below.

FIG. 1C shows a cross-sectional view of a further exemplarysemiconductor device 150 for use with one or more embodiments. Across-sectional view along line A-A′ in FIG. 1C may be similar as shownin FIG. 1B.

Semiconductor device 150 may be configured as a trench transistor andmay be to some degree similar to semiconductor device 100 describedabove. In particular, reference numerals which are the same as there maydenote the same or similar elements, which will thus not be described indetail again here. Reference is made to the description above.

Semiconductor device 150 differs from semiconductor device 100 in thatthe first insulating layer 110 may have a graded thickness in a region140 proximate the lower end of the gate electrode 109. As shown, thethickness of the first insulating layer 110 may increase in the region140 and may, for example, approach the thickness of the secondinsulating layer 112. This increase in the thickness may sometimes alsobe referred to as dielectric layer ramp (or oxide ramp in case of anoxide as insulating material).

FIG. 2 shows a cross-sectional view of a further exemplary semiconductordevice 200 for use with one or more embodiments. A cross-sectional viewalong line A-A′ in FIG. 2 may be similar as shown in FIG. 1B.

Semiconductor device 200 may be configured as a trench transistor andmay be to some degree similar to semiconductor devices 100 and 150described above. In particular, reference numerals which are the same asthere may denote the same or similar elements, which will thus not bedescribed in detail again here. Reference is made to the descriptionabove.

Semiconductor device 200 may include one or more contact trenches 115that may reach from the first side 106 of the semiconductor body 101into the semiconductor body 101. The contact trenches 115 may end in therespective body regions 108. The contact trenches 115 may be disposedbetween the trenches 130. For example, a contact trench 115 may in eachcase be disposed between the trenches 130 of two neighboring devicecells 120. The contact trench 115 may allow for electrically contactinga respective body region 108, for example by means of a highly dopedregion at the bottom of the contact trench 115. Furthermore, the contacttrench 115 may also allow for electrically contacting the first terminalelectrode regions 102, for example by means of highly doped regions atan upper part of the contact trench 115.

Contacting also the first terminal electrode regions 102 via the contacttrench 115 may, for example, be applied in cases where an integrationdensity may be so high that there may be not enough space to contact thefirst terminal electrode regions 102 from the surface.

FIG. 3 shows a cross-sectional view of a further exemplary semiconductordevice 300 for use with one or more embodiments.

Semiconductor device 300 may be configured as a trench transistorincluding a plurality of transistor cells 120 and may be to some degreesimilar to semiconductor devices 100, 150 and 200 described above. Inparticular, reference numerals which are the same as there may denotethe same or similar elements, which will thus not be described in detailagain here. Reference is made to the description above.

A transistor cell 120 in semiconductor device 300 may include two firsttrenches 130 and two second trenches 135 disposed next to each other inlateral direction of the semiconductor body 101. An additional electrode111 may be disposed in each of the first trenches 130, and a gateelectrode 109 may be disposed in each of the second trenches 135. Thegate electrodes 109 may be surrounded by respective first insulatinglayers 110, and the additional electrodes 111 may be surrounded byrespective second insulating layers 112. The first insulating layer 110may have the same thickness as the second insulating layer 112.Alternatively, the first insulating layer 110 and the second insulatinglayer 112 may have different thicknesses. For example, the firstinsulating layer 110 may be thinner than the second insulating layer112. The gate electrodes 109 may be disposed adjacent to first terminalelectrode regions 102. The first terminal electrode regions 102 may beconnected to a first terminal electrode 104, which may be disposed overa first side 106 of the semiconductor body 101. A second terminalelectrode 105 may be disposed over a second side 107 of thesemiconductor body 101, which may be opposite the first side 106. Thefirst side 106 may, for example, be a front side of the semiconductorbody 101 and the second side 107 may, for example, be a back side of thesemiconductor body 101. The second terminal electrode 105 may serve tocontact a second terminal electrode region 103, which may include ap-doped (e.g. highly p-doped, e.g. p+ doped) first subregion 103 aadjacent to the second terminal electrode 105 and an n-doped (e.g.lightly n-doped, e.g. n− doped) second subregion 103 b adjacent to thefirst subregion 103 a. A p-doped body region 108 may be formed betweenthe second terminal electrode region 103 (or the second subregion 103 bof the second terminal electrode region 103) and the first terminalelectrode regions 102. The gate electrodes 109 may extend along the bodyregion 108 as far as into the second terminal electrode region 103,starting from the first side 106 of the semiconductor body 101.Additional p-doped regions 116 may be formed between the gate electrodes109 and the additional electrodes 111 above the second terminalelectrode region 103 and below the first terminal electrode 104. Theadditional p-doped regions 116 may be insulated from the first terminalelectrode 104 by means of respective insulating layers 117.

Semiconductor device 300 may operate as an insulated-gate bipolartransistor (IGBT), due to the complementary doping of the first andsecond subregions 103 a, 103 b of the second terminal electrode region103.

Similarly as in semiconductor devices 100, 150, and 200, the additionalelectrodes 111 may shield the gate electrodes 109 and may prevent largefield strengths at the first insulating layers 110.

FIG. 4 shows a cross-sectional view of a further exemplary semiconductordevice 400 for use with one or more embodiments.

Semiconductor device 400 may be configured as a trench transistorincluding a plurality of transistor cells 120 and may be to some degreesimilar to semiconductor devices 100, 150, 200 and 300 described above.In particular, reference numerals which are the same as there may denotethe same or similar elements, which will thus not be described in detailagain here. Reference is made to the description above.

A transistor cell 120 in semiconductor device 400 may include two firsttrenches 130 and a second trench 135 disposed next to each other inlateral direction of the semiconductor body 101. Additional electrodes111 may be disposed in the first trenches 130, and a gate electrode 109may be disposed in the second trench 135 of the cell 120. The secondtrench 135 may be disposed laterally between the two first trenches 130.Each first trench 130 may be shared by two adjacent cells 120, as shownin FIG. 4, which shows three cells 120, i.e. a center cell 120 and twoneighboring cells 120 (only parts of the neighboring cells are shown).The gate electrode 109 may be surrounded by a first insulating layer110, and the additional electrodes 111 may be surrounded by respectivesecond insulating layers 112. The gate electrode 109 may be disposedadjacent to first terminal electrode regions 102. The first terminalelectrode regions 102 may be connected to a first terminal electrode104, which may be disposed over a first side 106 of the semiconductorbody 101. A second terminal electrode 105 may be disposed over a secondside 107 of the semiconductor body 101, which may be opposite the firstside 106. The first side 106 may, for example, be a front side of thesemiconductor body 101 and the second side 107 may, for example, be aback side of the semiconductor body 101. The second terminal electrode105 may serve to contact a second terminal electrode region 103, whichmay include an n-doped (e.g. highly n-doped, e.g. n+ doped) firstsubregion 103 a adjacent to the second terminal electrode 105 and ann-doped (e.g. lightly n-doped, e.g. n− doped) second subregion 103 badjacent to the first subregion 103 a. P-doped body regions 108 may beformed between the second terminal electrode region 103 (or the secondsubregion 103 b of the second terminal electrode region 103) and thefirst terminal electrode regions 102. The gate electrode 109 may extendalong the body regions 108 as far as into the second terminal electroderegion 103, starting from the first side 106 of the semiconductor body101. The additional electrodes 111 may extend along the body regions 108and along at least part of the second terminal electrode region 103(e.g., at least part of the second subregion 103 b of the secondterminal electrode region 103, as shown). Thus, the additionalelectrodes 111 may extend deeper into the semiconductor body 101 thanthe gate electrode 109. P-doped (e.g. highly p-doped, e.g. p+ doped)regions 118 may be formed adjacent to the first terminal electroderegions 102 in the p-doped body regions 108 and may be connected to thefirst terminal electrode 104. The p-doped regions 118 may serve toelectrically contact the body regions 108.

Similarly as in semiconductor devices 100, 150, 200, and 300, theadditional electrodes 111 may shield the gate electrode 109 and mayprevent large field strengths at the first insulating layer 110.

FIG. 5 shows a cross-sectional view of a further exemplary semiconductordevice 500 for use with one or more embodiments.

Semiconductor device 500 is configured as a trench transistor includinga plurality of transistor cells 120 and is to some degree similar tosemiconductor devices 100, 150, 200, 300 and 400 described above. Inparticular, reference numerals which are the same as there may denotethe same or similar elements, which will thus not be described in detailagain here. Reference is made to the description above.

A transistor cell 120 in semiconductor device 500 may include twotrenches 130 disposed next to each other in lateral direction of thesemiconductor body 101. An additional electrode 111 may be disposed ineach of the two trenches 130. A gate electrode 109 may be disposed overa first side 106 of a semiconductor body 101 between the two trenches130. The first side 106 may, for example, be a front side of thesemiconductor body 101. The gate electrode 109 may be insulated from thesemiconductor body 101 by first insulating layer 110. The additionalelectrodes 111 may be surrounded by respective second insulating layers112. P-doped body regions 108 may be formed in the semiconductor body101 on either side of the gate electrode 109 and may be partiallyoverlapped by the gate electrode 109. N-doped (e.g. highly n-doped, e.g.n+ doped) first terminal electrode regions 102 may be formed in the bodyregions 108 between the gate electrode 109 and a respective trench 130.

The first terminal electrode regions 102 may be connected to a firstterminal electrode 104, which may be disposed over the first side 106 ofthe semiconductor body 101. P-doped (e.g. highly p-doped, e.g. p+ doped)regions 118 may be formed adjacent to the first terminal electroderegions 102 in the p-doped body regions 108 and may be connected to thefirst terminal electrode 104. The highly p-doped regions 118 may serveto electrically contact the body regions 108.

A second terminal electrode 105 may be disposed over a second side 107of the semiconductor body 101, which may be opposite the first side 106.Second side 107 may, for example, be a back side of the semiconductorbody 101. The second terminal electrode 105 may serve to contact asecond terminal electrode region 103, which may include an n-doped (e.g.highly n-doped, e.g. n+ doped) first subregion 103 a adjacent to thesecond terminal electrode 105 and an n-doped (e.g. lightly n-doped, e.g.n− doped) second subregion 103 b adjacent to the first subregion 103 a.The p-doped body regions 108 may be formed between the second terminalelectrode region 103 (or the second subregion 103 b of the secondterminal electrode region 103) and the first terminal electrode regions102. The gate electrode 109 may extend along a horizontal direction andmay overlap parts of the body regions 108 and a part of the secondterminal electrode region 103 (or of the second subregion 103 b of thesecond terminal electrode region 103) between the body regions 108. Theadditional electrodes 111 may extend along the body regions 108 andalong at least part of the second terminal electrode region 103 (e.g.,at least part of the second subregion 103 b of the second terminalelectrode region 103, as shown). Thus, the additional electrodes 111 maybe formed in the trenches 130 and may extend vertically into thesemiconductor body 101 while the gate electrode 109 may be disposed overthe semiconductor body 101.

Similarly as in semiconductor devices 100, 150, 200, 300, and 400, theadditional electrodes 111 may shield the gate electrode 109 and mayprevent large field strengths at the first insulating layer 110.

Gate electrodes and/or additional electrodes of semiconductor devices,such as gate electrodes 109 and/or additional electrodes 111 ofsemiconductor devices 100, 150, 200, 300, 400, and 500, may contain orconsist of an electrically conductive material, for example polysiliconor a metal (or metal alloy), although other electrically conductivematerials may be possible as well. Insulating layers insulating the gateelectrodes 109 and/or additional electrodes 111, such as firstinsulating layer 110 and/or second insulating layer 112 of semiconductordevices 100, 150, 200, 300, 400, and 500, may contain or consist of anelectrically insulating material, for example an oxide, although otherelectrically insulating materials may be possible as well. Terminalelectrodes of semiconductor devices, such as first terminal electrode104 and/or second terminal electrode 105 of semiconductor devices 100,150, 200, 300, 400, and 500, may contain or consist of an electricallyconductive material such as, for example a metal or metal alloy,although other electrically conductive materials may be possible aswell.

Furthermore, it may be understood that the doping types of theindividual doped regions may be reversed to obtain devices of oppositeconductivity type, for example p-type field effect transistors insteadof n-type field effect transistors, or vice versa.

Semiconductor devices such as devices 100, 150, 200, 300, 400, and 500may have a stripe-like pattern or structure. For example, additionalelectrodes 111 and/or gate electrodes 109 of device cells 120 may have astripe-like pattern, as shown in FIG. 1B. However, it may be understoodthat semiconductor devices or device cells 120 of semiconductor devicesmay have differently shaped patterns or structures. For example, devicecells 120 of semiconductor devices may have an arbitrary shape ingeneral, for example a polygonal shape (e.g. triangular, quadrilateral,rectangular, square, hexagonal, or the like), a round shape (e.g.circular, elliptic, or the like), or an irregular shape.

In the following, reference will mainly be made to semiconductordevices, e.g. trench transistors, having electrodes made of polysilicon(also referred to as poly electrodes, or, short, polys) in the trench ortrenches. However, it is to be understood that the same or similarconsiderations may also hold true for devices with electrodes containingor consisting of other electrically conductive materials such as, e.g.,metals or metal alloys. Furthermore, dielectric or insulating layers inthe trench(es) will mainly be described as oxides or oxide layers, e.g.field oxide (FOX) or gate oxide (GOX). However, it is to be understoodthat the same or similar considerations may also hold true for otherdielectric or insulating materials.

Furthermore, although second terminal electrode 105 is shown as beingdisposed over the second side 107 of the semiconductor body 101, it maybe understood that second terminal electrode 105 may also be disposedover the first side 106 of semiconductor body 101 (not shown). In thiscase, first subregion 103 a of second terminal electrode region 103 may,for example, be configured as a buried layer and second terminalelectrode 105 disposed over the first side 106 may be electricallyconnected to the buried layer by means of a vertical contact (e.g.contact trench) extending from the first side 106 as far as to theburied layer.

Trench transistors such as e.g. transistors 100, 150, 200, 300, 400, and500 may be implemented as dense trench transistors. In one or moreembodiments, the term “dense trench transistor” may include or refer totrench transistors having a high or very high integration density, forexample including a large number (e.g. thousands, tens of thousands,hundreds of thousands, or millions, or even more) of transistor cells120. In one or more embodiments, the term “dense trench transistor” mayinclude trench transistors having a mesa width of less than or equal toabout 1.5 times a trench width. The term “mesa width” may, for example,include or refer to a width of a region between two trenches of twoadjacent device cells (e.g. width w_(m) in FIG. 1A). The term “trenchwidth” may, for example, include or refer to a width of a trench, inwhich the at least one additional electrode may be disposed (e.g. widthw_(t) in FIG. 1B). In one or more embodiments, the term “dense trenchtransistor” may include trench transistors having a mesa width of lessthan or equal to about 1.0 times the trench width. In one or moreembodiments, the term “dense trench transistor” may include trenchtransistors, in which an electrical breakdown occurs at the trenchbottom (in other words, in a region at or close to the bottom of thetrench(es)).

Trench transistors may sometimes be operated in a so-called avalanchepulse mode. Dense trench transistors may incorporate hot charge carriersinto the field dielectric (e.g. field oxide (FOX)), i.e. a dielectriclayer (e.g. oxide layer) insulating a field plate of the transistor(e.g. second insulating layer 112 in semiconductor devices 100, 150,200, 300, 400, and 500), (and/or into the gate dielectric (e.g. gateoxide (GOX)), i.e. a dielectric layer (e.g. oxide layer) insulating agate electrode of the transistor (e.g. first insulating layer 110 insemiconductor devices 100, 150, 200, 300, 400) during each avalanchepulse. This may lead to undesired drifting of device parameters, forexample breakdown voltage and/or starting voltage of the transistor,during repeated avalanche pulses (also referred to as repetitiveavalanche applications). In principle, this drifting may also causefilamentation effects (wherein a transistor current may be concentratedon only one or a few cells having a lower breakdown voltage than theremaining cells), which may lead to premature destruction of thedevices, which is illustrated in FIG. 6A.

FIG. 6A shows a diagram 600 plotting a trench transistor's breakdownvoltage Ubr versus a number of repetitive avalanche pulses, as a curve601.

It is shown that the breakdown voltage 601, starting from a so-called“zero hour” value, may initially rise (or drift) by a few volts withincreasing number of avalanche pulses (see region 602). Region 602 maybe seen as a stable operating region of the transistor. Then, after acritical number of avalanche pulses, the drifting direction of thebreakdown voltage 601 may be reversed and the breakdown voltage 601 maydecrease noticeably (see region 603). Region 603 may be seen as anoperating region of the transistor, which may be unstable in principle.For a failure-free operation, it may be desirable that a transistornever reaches the falling region of the breakdown voltage 601 (region603).

Another problem may occur when one or more individual transistor cellsreach the falling mode significantly earlier than others, e.g. due tolocal faulty processing (defect density in e.g. trench or contact holephoto technique levels), as these (defective) cells may form localfilaments, which may render the whole transistor unusable, which isillustrated in FIG. 6B.

FIG. 6B shows a diagram 650 plotting a breakdown voltage Ubr versus anumber of repetitive avalanche pulses for two different types oftransistor cells: a first curve 651 a shows the breakdown voltage ofnormal (non-defective) cells (e.g. of a cell field including a largenumber (e.g. millions) of normal (non-defective) cells), while a secondcurve 651 b shows the breakdown voltage of one or more (e.g. a few)defective transistor cells.

The term “defective cell” as used herein may, for example, include orrefer to a cell that contains at least one defect or cell defect, forexample a trench defect or contact trench defect. The term“non-defective cell” as used herein may, for example, include or referto a cell that is free of defects.

The term “defect” as used herein may, for example, include or refer to asubstantial deviation from a normal (or standard, or desired, orpre-determined) condition, state, shape and/or structure of a certainentity (e.g. element, structure, layer, etc.). For example, the term“trench defect” may include or refer to a substantial deviation of theshape or structure of a trench, or of one or more elements of the trenchor in the trench, e.g. an electrode or dielectric in the trench. Forexample, the term “trench defect” may include a case, where a dimension(e.g. depth) of a trench substantially deviates from a desired dimension(e.g. depth), e.g. a trench depth that is too deep. Further, the term“trench defect” may include a case where a dimension of an element in atrench (e.g. a thickness of an insulating layer, e.g. gate dielectric(e.g. GOX), or field plate dielectric (e.g. FOX)) substantially deviatesfrom a desired dimension (e.g. desired thickness), e.g. an oxidethickness that is too thin. Further, the term “trench defect” mayinclude a case where an element in the trench, which was supposed to bepresent (e.g. an electrode, e.g. shield electrode, e.g. field plate), isactually missing, e.g. a missing poly electrode in the trench. Exemplarydefects are also shown and described further below in connection withFIG. 9.

Defects as mentioned above may, for example, lead to a substantialdeviation in the functionality, characteristics and/or behavior of therespective entity, compared with the functionality, characteristics orbehavior of similar entities having no defects. For example, a defect ina transistor cell (e.g. trench defect, e.g. substantial thinning of aFOX) may lead to a substantial deviation in the transistor cell'sbehavior compared to other (non-defective) cells.

For example, as shown in FIG. 6B, the breakdown voltage 651 b ofdefective transistor cell(s) may reach the falling region earlier (i.e.after a smaller number of avalanche pulses) than the breakdown voltage651 a of normal (non-defective) cell(s). This may lead to an increasingvoltage difference ΔV (indicated by arrow 652) between the breakdownvoltage of the defective cell(s) 651 b and the breakdown voltage of thenon-defective cells 651 a. The higher this voltage difference 652between the defective cell(s) and the remaining cell field becomes, themore critical the situation may become. Thus, if no further measures aretaken, it may be possible that only relatively few avalanche pulses maybe carried out with the transistor.

Therefore, it may be desirable to detect defective transistor cellsduring a pre-test of the transistor, for example in order to preventdefective devices from being delivered to customers.

Up to now, there are no reliable electrical detection methods to detectindividual defective transistor cells, which may have formed as a resultof trench defects or contact trench defects in trench transistors suchas dual-poly trench transistors (i.e. trench transistors having two polyelectrodes, namely a poly gate electrode (herein also referred to asPoly-G) and an additional poly electrode (herein also referred to asPoly-S) acting as a shield electrode and typically coupled with thetransistor source during normal operation of the transistor, in order tofilter out defective transistors. Structural inline detection methodsmay be very time-consuming and may show a reliable filtering only fordefects of a certain minimum size, e.g. defects having a minimum size ofat least 1 μm, for example significantly larger than 3 μm.

One or more embodiments may provide test methods and arrangements fortesting semiconductor devices, in particular trench devices such astrench transistors (e.g. dense trench transistors, e.g. trench fieldeffect transistors (FETs), e.g. trench MOSFETs, or trench insulated-gatebipolar transistors (IGBTs)) containing a plurality of device cells(e.g. transistor cells), to detect defective devices, for exampledevices having defects (e.g. trench defects) in one or more devicecells. For example, trench transistors 100, 150, 200, 300, 400, and 500described herein above may be seen as illustrative examples forsemiconductor devices, to which test methods and/or test arrangements inaccordance with one or more embodiments may be applied. However, as willbe readily understood, test methods and/or test arrangements inaccordance with one or more embodiments described herein may also applyto other trench devices, e.g. other trench transistors, for exampletrench transistors with three or more electrodes in one trench.

One or more embodiments may implement so-called defect density scansand/or reliability scans by providing corresponding test structures orarrangements and test methods, in which trench devices (such as trenchtransistors) having a plurality of electrodes (e.g. polysiliconelectrodes (polys)), for example a gate electrode and one or moreadditional electrodes (e.g. a shield electrode, e.g. a field plate), inthe trench may be electrically scanned for defects and/or quality of oneor more trench dielectrics (e.g. oxides), for example the quality of afield oxide (FOX) and/or a gate oxide (GOX) and/or an inter-electrodeoxide (e.g. oxide between two polys (POLOX)). Thus, in accordance withone or more embodiments, defective devices may be detected and filteredout at the end of the front end, e.g. on wafer level, so that it may,for example, be prevented that the defective products are delivered to acustomer. In one or more embodiments, corresponding device (e.g.transistor) structures and/or pad structures and/or wiring structuresand/or scan or test procedures may be provided, that may enable theaforementioned defect detection and/or filtering of defective devices orproducts.

One or more embodiments may provide structures or methods, which mayallow for detecting and filtering out defective transistor cells, whichmay affect the breakdown voltage of the transistor. Thus, it may, forexample, be possible to prevent defective devices from being deliveredto customers.

Conventionally, dual-poly transistors may be internally connected insuch a manner that the lower poly in the trench (field plate poly, orso-called “Poly-S”), e.g. electrode 111 in FIG. 1A, may be always at thesource potential and may be, by means of the chip layout, directlyconnected with a power source metal pad via a contact hole.

In accordance with one or more embodiments, dual-poly transistors may beprovided, in which the aforementioned field plate poly initially (e.g.up to and including front end measurements) may be led out separately toone or more pads that may be contacted separately. This may allow forgeneral measurements or tests to be carried out in the front end (e.g.by means of probe cards, etc.), which may test the reliability oftransistor cells and/or if or which transistor cells are affected bydefects, before these separate pads may afterwards be connected with thesource pad (or, more generally, with a pad that carries a desired ortarget potential) in the back end assembling.

In one or more embodiments, connecting the separate pad(s) to the sourcepad (or, the pad carrying the target potential) may be achieved in asimple manner e.g. by means of wire bonding and/or clip bonding, and/oranti-fuse techniques and/or metal rewiring or redistribution techniquesusing material deposition or laser cut, and/or other suitabletechniques. For example, in case that the separate pad(s) is/areconnected to the large source pad of a power transistor in the back endassembly, the final device or product may have the same potentialcharacteristics and thus the same operating characteristics as aclassical device or product.

One or more embodiments may include one or more of the following: a)disconnecting or undoing a direct contact of a poly electrode in atrench (e.g. Poly-S), b) providing a separate pad on a chip surface, c)forming a direct contact between the pad and the poly electrode in thetrench, d) carrying out one or more defect scans and/or reliabilitytests e.g. in the front end (e.g. using one or more probes, e.g. a probecard), e) (optionally) evaluating data obtained by the test(s) by meansof an evaluation scheme or algorithm such as dynamical PAT (part averagetesting) for filtering out systems that are defective or deviate fromnominal values, f) (optionally) inking on wafer level and (optionally)delivering bare dies to customers, g) back end assembly, includingformation of at least one conductive connection between the separate padand a pad on the chip having a desired (target) potential (for example,connecting separate Poly-S pad with a power source pad on the chip formaking contact to the source potential if the source potential is thedesired potential, or (e.g. for high-speed or low-speed variants)connecting the separate Poly-S pad with a gate pad on the chip formaking contact to the gate potential if the gate potential is thedesired potential (in this case, the gate pad may, for example, besuitably enlarged), h) forming the aforementioned conductive connection(electrical contact) by means of bonding with one or more bond wiresand/or a clip and/or anti-fuse techniques and/or metal rewiring orredistribution techniques using material deposition or laser cut and/orother suitable techniques, i) testing of the now restored normaltransistor functions in the back end.

In one or more embodiments, a Poly-S voltage (in other words, a voltageapplied to Poly-S electrodes) may be tuned during one or morelow-current breakdown voltage measurements, such that various breakdownregimes may be tested (e.g. low-current parabola measurement). Forexample, the x-axis (i.e., axis pointing to the right) in diagram 650 ofFIG. 6B may also represent the applied Poly-S bias voltage in a defectdensity scan, which (in the example shown in FIG. 6B) may detect aconsiderable deviation of the breakdown voltage Ubr from the nominal ordesired value (represented by curve 651 a) at a bias voltage of about +Xvolts (as shown) and may thus filter out the defective device. In otherwords, the occurrence of a deviation of the measured breakdown voltagefrom a nominal or desired breakdown voltage at a certain value (e.g. +Xvolts, as shown) of the Poly-S bias voltage may indicate that the testeddevice (or, one or more device cells) may include one or more defects.

In one or more embodiments, a FOX defect density stress test may becarried out, which may be similar to a GOX stress test. This may includegradually increasing a Poly-S potential with respect to all remainingpotentials (e.g. potentials at source, drain and other gates of thetransistor), which remain at ground (e.g. 0 V). For example, inaccordance with one or more embodiments, a FOX defect density stresstest may include applying a high potential to the Poly-S electrode, i.e.a potential which is high compared to the entire rest (which may be atground, e.g. 0 V), in order to measure a tunnel current as a measure fora possibly defective thin part in the FOX, which may then be filteredout. In case of a particularly distinct thin part this may even lead todestruction of the FOX, so that the device (e.g. transistor) may then befiltered out with certainty. Alternatively, a voltage, which is negativecompared to source, may be applied to the Poly-S electrode, and apositive voltage may simultaneously be applied to drain. Thus, in one ormore embodiments, a trench bottom may be stressed more while a voltagemay be reduced in a region of an oxide ramp, if necessary.

In one or more embodiments, a direct test of an inter-electrodedielectric (in other words, a dielectric layer between two electrodes inthe trench), for example an oxide layer between two poly electrodes(herein also referred to as POLOX layer), may be carried out. Forexample, in accordance with some embodiments, Poly-G may be testedversus Poly-S. In other words, an inter-electrode dielectric betweenPoly-G and Poly-S may be tested for thin parts. The test procedure maybe similar as in the FOX test, with the voltage being applied betweenthe two electrodes (e.g. poly electrodes (polys), e.g. Poly-G andPoly-S) in the trench.

In one or more embodiments, two or three, or even more, electrodes (e.g.polys) in the trench may be tested in a similar manner as describedabove. In particular, an inter-electrode dielectric (e.g.inter-electrode oxide) between a respective electrode pair (e.g. polypair) may be tested for thin parts.

In accordance with one or more embodiments, for example in case ofhigh-speed or low-speed devices or products, electrodes (e.g. polyelectrodes) in the trench, which may have the same potential in thefinal product, may be tested against each other.

In accordance with one or more embodiments, the test described hereinmay also be applied to sensor structures or devices.

In accordance with one or more embodiments, a Poly-S may (still) beseparately bonded on product level. In this case, if a suitable Poly-Svoltage is applied, pulsed high-current single or repetitive avalanchetests may be carried out, which may be very sensitive to defects, whichmay be, for example, not noticeable at all in conventional singleavalanche tests (where Poly-S voltage=0 V). This may be a further way tofilter or sort out defective devices or components by means ofmeasurement. In the product, the required Poly-S potential or voltagemay, for example, be applied in a circuitry-wise manner, or via fuses,zap diodes, or other suitable ways. This may also have the effect thatdevices or components may be analyzed with respect to their defectcharacteristics, after avalanche stress, annealing, or other stresstests.

An aspect of test arrangements and methods in accordance with one ormore embodiments may be seen in that an arbitrary trench, which maycarry an arbitrary electrical potential in the final product, may betested for various reliability criteria (such as dielectric layer (e.g.oxide) thickness or breakdown voltage) in an intermediate stage. Byusing a suitable arrangement, also a semiconductor region between two ormore selected trenches (e.g. a drift zone, an accumulation zone, etc.)may be tested in accordance with one or more embodiments. For example, adefect scan similar to a tomography of a human being may be possible byusing separately controllable electrodes and varying various potentials(e.g. continuously) within predeterminable value ranges. Separatecontrolling of the electrode potentials may, for example, be achieved byproviding one or more additional pads, which may be coupled to therespective electrodes.

In one or more embodiments, a shield electrode (e.g. field plate poly)may be not directly connected to a source pad via one or more contactholes, but at least one bond wire (or other connection structures) maybe involved in establishing the electrical connection. For example, anelectrode (e.g. poly), or also a semiconductor region, to be tested maybe located structurally completely separate or isolated from theremaining chip construction and may be connected with the remaining chipconstruction by means of one or more electrical connections addedafterwards (e.g. only after testing).

FIG. 7A shows a test method 700 according to various embodiments.

In 702, a semiconductor device to be tested may be provided. Thesemiconductor device may include at least one device cell. The at leastone device cell may include at least one trench, at least one firstterminal electrode region and at least one second terminal electroderegion, at least one gate electrode, and at least one additionalelectrode disposed at least partially in the at least one trench. Anelectrical potential of the at least one additional electrode may becontrolled separately from electrical potentials of the at least onefirst terminal electrode region, the at least one second terminalelectrode region and the at least one gate electrode. For example, theat least one additional electrode may be electrically disconnected orinsulated from the at least one first terminal electrode region, the atleast one second terminal electrode region and the at least one gateelectrode.

In 704, at least one electrical test potential may be applied to atleast the at least one additional electrode to detect defects in the atleast one device cell.

In one or more embodiments, the semiconductor device may be formed in ormay be part of a semiconductor workpiece, for example a wafer or a chip.

In one or more embodiments, the semiconductor workpiece may include atleast one pad, for example a plurality of pads. In one or moreembodiments, the semiconductor workpiece may include at least one firstpad electrically connected to the at least one first terminal electroderegion. In one or more embodiments, the semiconductor workpiece mayinclude at least one second pad electrically connected to the at leastone second terminal electrode region. In one or more embodiments, thesemiconductor workpiece may include at least one third pad electricallyconnected to the at least one gate electrode. In one or moreembodiments, the semiconductor workpiece may include at least one fourthpad electrically connected to the at least one additional electrode.

In one or more embodiments, the semiconductor workpiece may include atleast one separate pad assigned to the at least one additionalelectrode. Thus, a potential of the at least one additional electrodemay be controlled separately from potentials of other electrodes. Inother words, the potential of the at least one additional electrode maybe changed without changing potentials of other electrodes or electroderegions (e.g. gate electrode potential, and/or source/drain potential).

In one or more embodiments, the pads may be separate pads. In one ormore embodiments, the pads may be electrically disconnected from oneanother.

In one or more embodiments, at least one of the pads may include or mayconsist of an electrically conductive material, for example a metal ormetal alloy.

In one or more embodiments, at least one of the pads may be disposed ator over a front side of the semiconductor workpiece. In one or moreembodiments, at least one of the pads may be disposed at or over a backside of the semiconductor workpiece.

In one or more embodiments, the semiconductor workpiece may include asemiconductor body, wherein the at least one trench may be formed in orextend into the semiconductor body.

In one or more embodiments, the semiconductor body may include orconsist of silicon, although other semiconductor materials, includingcompound semiconductor materials, may be used in accordance with otherembodiments.

In one or more embodiments, the at least one test potential may beconfigured to detect trench defects in the at least one device cell.

In one or more embodiments, the semiconductor device may include aplurality of device cells, for example hundreds of device cells, orthousands of device cells, or ten thousands of device cells, or hundredsof thousands of device cells, or millions of device cells, or even moredevice cells. In one or more embodiments, the device cells may beconfigured or arranged as a cell field.

In one or more embodiments, the plurality of device cells may all beconfigured substantially in the same way, for example may all havesubstantially the same structure, for example may all have substantiallythe same elements or regions.

In one or more embodiments, the at least one electrical potential may beapplied to at least part of the cells simultaneously.

In one or more embodiments, the at least one electrical potential may beapplied to all cells simultaneously.

In one or more embodiments, the at least one electrical potential may beapplied to at least one common electrode connected to all cells.

In one or more embodiments, the at least one electrical test potentialmay be configured to detect defects in the plurality of device cells,for example trench defects and/or contact trench defects.

In one or more embodiments, the at least one electrical test potentialmay be configured to detect one or more defective device cells among theplurality of device cells of the semiconductor device.

In one or more embodiments, the first terminal electrode region may beconfigured to receive a first power supply potential during normaloperation of the semiconductor device, for example a lower power supplypotential or an upper power supply potential, e.g. a source/drainpotential, e.g. a source potential, or an emitter/collector potential,e.g. an emitter potential.

In one or more embodiments, the second terminal electrode region may beconfigured to receive a second power supply potential during normaloperation of the semiconductor device, for example an upper power supplypotential or a lower power supply potential, e.g. a source/drainpotential, e.g. a drain potential, or an emitter/collector potential,e.g. a collector potential.

In one or more embodiments, the semiconductor device may be configuredas a transistor, for example as a field-effect transistor (FET), e.g. aMOSFET (e.g. NMOS or PMOS), or as a bipolar transistor, e.g. aninsulated-gate bipolar transistor (IGBT).

In one or more embodiments, the at least one first terminal electroderegion may include or be a first source/drain region, for example asource region or a drain region.

In one or more embodiments, the at least one second terminal electroderegion may include or be a second source/drain region, for example adrain region or a source region.

In one or more embodiments, the at least one first terminal electroderegion may include or be a first emitter/collector region, for examplean emitter region or a collector region.

In one or more embodiments, the at least one second terminal electroderegion may include or be a second emitter/collector region, for examplea collector region or an emitter region.

In one or more embodiments, the transistor may be configured as a trenchtransistor.

In one or more embodiments, the transistor may be configured as a powertransistor.

In one or more embodiments, the at least one gate electrode may beconfigured to control a switching state of the semiconductor device,e.g. a switching state of the transistor.

In one or more embodiments, the at least one gate electrode may bedisposed at least partially in the at least one trench.

In one or more embodiments, the at least one gate electrode and the atleast one additional electrode may be disposed at least partially in theat least one trench.

In one or more embodiments, the at least one gate electrode and the atleast one additional electrode may be disposed in the same trench. Inone or more embodiments, the at least one gate electrode may be disposedin an upper portion of the trench and the at least one additionalelectrode may be disposed in a lower portion of the trench below the atleast one gate electrode. In one or more embodiments, the at least onegate electrode and the at least one additional electrode in the trenchmay be insulated from one another, for example by means of an insulatinglayer or inter-electrode dielectric, for example an oxide layer.

In one or more embodiments, the at least one gate electrode and the atleast one additional electrode may be disposed laterally next to eachother in the at least one trench. In one or more embodiments, the atleast one additional electrode may extend deeper in the trench than thegate electrode.

In one or more embodiments, the at least one gate electrode and the atleast one additional electrode may be disposed in different trenches.

In one or more embodiments, the at least one cell may include at leastone first trench and at least one second trench, wherein the at leastone additional electrode may be disposed in the at least one firsttrench and the at least one gate electrode may be disposed in the atleast one second trench.

In one or more embodiments, the at least one gate electrode may bedisposed over the semiconductor body, for example over a front side ofthe semiconductor body.

In one or more embodiments, the at least one gate electrode may beinsulated from the semiconductor body. In one or more embodiments, thesemiconductor device may include at least one first insulating layer toinsulate the at least one gate electrode. In one or more embodiments,the at least one first insulating layer may at least partially surroundthe at least one gate electrode. In one or more embodiments, the atleast one first insulating layer may include or consist of an oxide. Inaccordance with other embodiments, the at least one first insulatinglayer may contain or consist of other insulating materials.

In one or more embodiments, the at least one additional electrode may beconfigured as a shield electrode, for example as a field plate.

In one or more embodiments, the at least one additional electrode may beinsulated from the semiconductor body and/or the gate electrode. In oneor more embodiments, the semiconductor device may include at least onesecond insulating layer to insulate the at least one additionalelectrode. In one or more embodiments, the at least one secondinsulating layer may be disposed in the at least one trench. In one ormore embodiments, the at least one second insulating layer may at leastpartially surround the at least one additional electrode. In one or moreembodiments, the at least one second insulating layer may include orconsist of an oxide. In accordance with other embodiments, the at leastone second insulating layer may contain or consist of other insulatingmaterials.

In one or more embodiments, the at least one gate electrode may includeor may consist of an electrically conductive material, for examplepolysilicon or a metal or metal alloy, although electrically conductivematerials may be used in accordance with other embodiments.

In one or more embodiments, the at least one additional electrode mayinclude or may consist of an electrically conductive material, forexample polysilicon or a metal or metal alloy, although electricallyconductive materials may be used in accordance with other embodiments.

In one or more embodiments, the semiconductor device may include or beconfigured in accordance with one or more features described inconnection with one or more of semiconductor devices 100, 150, 200, 300,400, and 500.

In one or more embodiments, applying at least one test potential to atleast the at least one additional electrode may include applying aplurality of test potentials to the at least one additional electrode,for example a sequence of increasing test potentials (in other words, asequence of test potentials, each test potential having a fixedmagnitude, and the magnitudes increasing from test potential to testpotential, i.e. V1<V2<V3< . . . <Vn−1<Vn, with Vi being the i-thpotential of the sequence), or a sequence of decreasing test potentials(in other words, a sequence of test potentials, each test potentialhaving a fixed magnitude, and the magnitudes decreasing from testpotential to test potential, i.e. V1>V2>V3> . . . >Vn−1>Vn, with Vibeing the i-th potential of the sequence).

In one or more embodiments, applying at least one test potential to atleast the at least one additional electrode may include applying aplurality of different test potentials to the at least one additionalelectrode while applying a fixed potential (for example, groundpotential, e.g. 0 V) to the at least one gate electrode, the at leastone first terminal electrode region and the at least one second terminalelectrode region. For example, applying at least one test potential toat least the at least one additional electrode may include ramping up apotential at the at least one additional electrode while maintaining thepotentials of the at least one first terminal electrode region, the atleast one second terminal electrode region and the gate electrode at afixed value, e.g. ground, e.g. 0 V.

In one or more embodiments, the method may include applying the at leastone test potential to at least the at least one additional electrode andmeasuring a tunnel current through the at least one second insulatinglayer. In other words, the at least one test potential may be configuredto measure a tunnel current through the at least one second insulatinglayer.

In one or more embodiments, the method may include applying the at leastone test potential to at least the at least one additional electrode anddetermining a breakdown voltage of the semiconductor device. In otherwords, the at least one test potential may be configured to determine abreakdown voltage of the semiconductor device.

In one or more embodiments, applying the at least one test potential toat least the at least one additional electrode may include carrying outone or more breakdown voltage measurements, for example low-currentbreakdown voltage measurements, with varying bias voltages at the atleast one additional electrode, e.g. a low-current parabola measurement.In one or more embodiments, the bias voltage may be varied (e.g. ramped)from a lower bias voltage to an upper bias voltage, which is higher thanthe lower bias voltage. In one or more embodiments, the lower biasvoltage may be about −20 V and the upper bias voltage may be about +50V. In one or more embodiments, the lower bias voltage may be about −5 Vand the upper bias voltage may be about +25 V. In one or moreembodiments, the lower bias voltage may be about 0 V and the upper biasvoltage may be about +12 V.

In one or more embodiments, each breakdown voltage measurement (i.e.,for each value of the bias voltage at the at least one additionalelectrode) may include ramping up a potential at the at least one secondterminal electrode region (e.g. drain region) while applying a fixedpotential (e.g. ground potential, e.g. 0 V) to the at least one gateelectrode and the at least one first terminal electrode region (e.g.source region), and measuring an electric current flowing between the atleast one first terminal electrode region (e.g. source region) and theat least one second terminal electrode region (e.g. drain region). Thepotential at the at least one second terminal electrode region (e.g.drain region) may, for example, be ramped up starting from a lower valueU_(lower) (e.g. 0 V) until a desired value of the electric current (e.g.1 mA) is measured at some upper value U_(upper) of the potential. Thedifference between the potential U_(upper) at the at least one secondterminal electrode region and the potential at the at least one firstterminal electrode region (e.g. ground potential, e.g. 0 V) may thenindicate the breakdown voltage Ubr corresponding to the respective biasvoltage at the at least one additional electrode. By carrying outbreakdown voltage measurements for a number of different bias voltagesat the at least one additional electrode, the dependence of thebreakdown voltage on the bias voltage may be determined, which may, forexample, look similar to one of the curves shown in FIG. 6A and FIG. 6B.

In one or more embodiments, at least one of the at least one firstterminal electrode region and the at least one second terminal electroderegion may include or be configured as a contact trench region.

In one or more embodiments, the at least one test potential may beconfigured to detect one or more defects in the contact trench region orregions.

In one or more embodiments, applying the at least one test potential toat least the at least one additional electrode may include subjectingthe semiconductor device to at least one of a defect density scan and areliability scan.

In one or more embodiments, applying the at least one test potential toat least the at least one additional electrode may include subjectingthe semiconductor device to a field oxide (FOX) stress test.

In one or more embodiments, applying at least one test potential to atleast the at least one additional electrode may include forcing apredeterminable electrical current through the semiconductor device(e.g. transistor). The electrical current may have a constant orsubstantially constant current density. For example, the current densityof the electrical current may be held constant or substantially constantfor a predeterminable time period.

In one or more embodiments, the current density may be greater than orequal to about 0.5 A/mm² (amps per mm² of active device area), forexample greater than or equal to about 10 A/mm², for example greaterthan or equal to about 50 A/mm², for example greater than or equal toabout 100 A/mm² In one or more embodiments, the current density may benear a destruction limit of the device (e.g. transistor).

In one or more embodiments, applying at least one test potential to atleast the at least one additional electrode may include carrying out anavalanche test.

In one or more embodiments, the avalanche test may include applying oneor more avalanche pulses to the semiconductor device. In other words,the avalanche test may be a pulsed avalanche test.

In one or more embodiments, the method may further include analyzingtest results obtained from testing the semiconductor device. In one ormore embodiments, analyzing or evaluating the test results may includeor be achieved by an evaluation scheme or algorithm such as dynamicalpart average testing (PAT).

In one or more embodiments, applying the at least one test potential toat least the at least one additional electrode may include or may becarried out using one or more probes, for example using a probe cardincluding one or more probes. The probes may, for example, contact oneor more contact pad(s) connected to the at least one first and secondterminal electrode regions, the at least one gate electrode, and the atleast one additional electrode.

In one or more embodiments, applying the at least one test potential toat least the at least one additional electrode may be carried out duringor at the end of a front end processing stage.

In one or more embodiments, the at least one additional electrode may beelectrically connected to the at least one first terminal electroderegion (e.g. source region), or to the at least one gate electrode,after applying the at least one test potential, for example aftercarrying out one or more of the tests described herein. Connecting theat least one additional electrode to the at least one first terminalelectrode region or to the at least one gate electrode may, for example,be achieved by forming an electrical connection between respective pads,e.g. between a pad coupled to the at least one additional electrode anda pad coupled to the at least one first terminal electrode region (e.g.source pad) or a pad coupled to the at least one gate electrode (gatepad).

In one or more embodiments, the semiconductor device may have a surfacearea (e.g. chip area) of greater than or equal to about 1 mm², forexample greater than or equal to about 2 mm², for example greater thanor equal to about 5 mm², for example greater than or equal to about 10mm², for example greater than or equal to about 20 mm².

FIG. 7B shows a test method 750 according to various embodiments.

In 752, a workpiece may be provided. The workpiece may include atransistor to be tested. The transistor may include a plurality of cellselectrically connected in parallel. Each cell may include at least onetrench, at least one first terminal electrode region and at least onesecond terminal electrode region, at least one gate electrode, and atleast one additional electrode disposed at least partially in the atleast one trench, wherein an electrical potential of the at least oneadditional electrode may be controlled separately from electricalpotentials of the at least one first terminal electrode region, the atleast one second terminal electrode region and the at least one gateelectrode.

In 754, a plurality of test potentials may be applied to at least the atleast one additional electrode of the cells to detect defective cellsamong the plurality of cells.

Method 750 may further be configured in accordance with one or moreembodiments described herein.

Test methods in accordance with one or more embodiments, for examplemethod 700 and/or method 750, may, for example, be carried out by a testarrangement such as test arrangement 800′ shown in FIG. 8.

FIG. 8 shows a test arrangement 800′ in accordance with variousembodiments.

Test arrangement 800′ may include a semiconductor device 800 to betested. Semiconductor device 800 may include at least one device cell120. The at least one device cell 120 may include at least one trench130. The at least one device cell 120 may further include at least onefirst terminal electrode region 102. The at least one device cell 120may further include at least one second terminal electrode region 103.The at least one device cell 120 may further include at least one gateelectrode 109. The at least one device cell 120 may further include atleast one additional electrode 111. The at least one additionalelectrode 111 may be disposed at least partially in the at least onetrench 130. An electrical potential of the at least one additionalelectrode 111 may be controlled separately from electrical potentials ofthe at least one first terminal electrode region 102, the at least onesecond terminal electrode region 103 and the at least one gate electrode109.

Test arrangement 800′ may further include a test device 850. Test device850 may be configured to apply at least one electrical test potential toat least the at least one additional electrode 111 to detect defects inthe at least one device cell 120.

In one or more embodiments, test device 850 may be electrically coupledor connected to semiconductor device 800, for example by means of one ormore electrical connections 851, 852, 853, 854.

For example, test device 850 may be coupled to the at least one firstterminal electrode region 102 via a first electrical connection 851. Inone or more embodiments, first electrical connection 851 may, forexample, include an electrical connection between test device 850 and afirst pad (e.g. first chip pad, e.g. a source pad) of semiconductordevice 800 coupled to the at least one terminal electrode region 102 (orto a first terminal electrode coupled to the at least one terminalelectrode region 102).

For example, test device 850 may be coupled to the at least one secondterminal electrode region 103 via a second electrical connection 852. Inone or more embodiments, second electrical connection 852 may, forexample, include an electrical connection between test device 850 and asecond pad (e.g. second chip pad, e.g. drain pad) of semiconductordevice 800 coupled to the at least one second terminal electrode region102.

For example, test device 850 may be coupled to the at least one gateelectrode 109 via a third electrical connection 853. In one or moreembodiments, third electrical connection 853 may, for example, includean electrical connection between test device 850 and a third pad (e.g.third chip pad, e.g. gate pad) of semiconductor device 800 coupled tothe at least one gate electrode 109.

For example, test device 850 may be coupled to the at least oneadditional electrode 111 via a fourth electrical connection 854. In oneor more embodiments, fourth electrical connection 854 may, for example,include an electrical connection between test device 850 and a fourthpad (e.g. fourth chip pad) of semiconductor device 800 coupled to the atleast one additional electrode 111.

In one or more embodiments, semiconductor device 800 may be formed in orbe part of a chip or wafer. In one or more embodiments, at least one ofthe pads may be disposed over a front side of the chip or wafer. In oneor more embodiments, at least one of the pads may be disposed over aback of the chip or wafer.

In one or more embodiments, semiconductor device 800 may be configuredas a transistor, for example as a field effect transistor (FET), e.g.MOSFET, or as a bipolar transistor, e.g. an insulated-gate bipolartransistor (IGBT).

Semiconductor device 800, or one or more elements of semiconductordevice 800 may, for example, be further configured in accordance withone or more embodiments described herein, for example in accordance withone more embodiments described in connection with method 700, and/or inaccordance with one or more features described in connection with one ormore of semiconductor devices 100, 150, 200, 300, 400, and 500.

In one or more embodiments, test device 850 may include or may be a testcircuit. In one or more embodiments, test device 850 may include or maybe test equipment. In one or more embodiments, test device 850 mayinclude one or more probes, for example a probe card including one ormore probes. The probe(s) or probe card may, for example, serve tocontact one or more pads electrically connected with one or moreelectrodes or electrode regions of semiconductor device 800, for exampleone or more of first to fourth pads described above.

In one or more embodiments, test device 850 may be configured to performone or more tests or test methods in accordance with one or moreembodiments described herein, for example a defect density scan and/or areliability scan. To this end, test device 850 may be configured toapply one or more, e.g. a plurality of, test potentials to at least theat least one additional electrode 111. In one or more embodiments, testdevice 850 may, for example, be configured to apply a sequence ofincreasing or decreasing potentials to at least the at least oneadditional electrode 111. In one or more embodiments, test device 850may, for example, be configured to force a predeterminable electriccurrent through semiconductor device 800. In one or more embodiments,test device 850 may, for example, be configured to carry out anavalanche test, e.g. a pulsed avalanche test.

In one or more embodiments, test device 850 may be configured toevaluate test results obtained (e.g. measured breakdown voltages), forexample by using an evaluation scheme or algorithm such as e.g. partaverage testing (PAT).

FIG. 9 shows a semiconductor device 900 having various cell defects, andfurther shows an electrical scan curve, for illustrating aspects of oneor more embodiments.

Semiconductor device 900 may include a plurality of device cells 120.Each cell may include a trench 130. The trenches 130 may be formedwithin or extend into a semiconductor body 101. The trenches 130 may beconfigured to include a gate electrode 109 and an additional electrode111 disposed in the respective trench 130. Gate electrode 109 may beinsulated by a first insulating layer (e.g. gate oxide (GOX)), andadditional electrode 111 may be insulated by a second insulating layer(e.g. field oxide (FOX)). Gate electrode 109 may serve to control aswitching state of semiconductor device 900, while the additionalelectrode 111 may, for example, serve as a shield electrode to reduce anelectric field intensity at the gate dielectric 110 insulating the gateelectrode 109. A contact trench 115 may in each case be disposed betweentwo neighboring trenches 130. Semiconductor device 900 may includefurther elements, for example first terminal electrode regions (e.g.source regions) disposed between the contact trenches 115 and thetrenches 130, or at least one second terminal electrode region, and/orother elements (not shown for sake of clarity).

Three different cell defects 901, 902, 903 are shown as an example. Afirst cell defect may be a defect in a trench 130, namely that athickness of the second insulating layer (e.g. FOX) insulating theadditional electrode 111 substantially deviates from a desiredthickness, in particular a considerable thinning of the secondinsulating layer (e.g. FOX) e.g. at the bottom of the trench 130, asindicated by encircled region 901. A second cell defect may be anotherdefect of a trench 130, namely that the additional electrode 111 ismissing in the trench 130, as indicated by encircled region 902. A thirdcell defect may be a defect of a contact trench 115, namely that a depthof the contact trench 115 is too deep, as illustrated by encircledregion 903.

Cell defects 901, 902, and/or 903 may lead to a substantial deviation inthe behavior of the corresponding cell or cells 120 compared to other(non-defective) cells 120, which may have a negative impact on theperformance of semiconductor device 900, or may even rendersemiconductor device 900 unusable, as described above.

Test methods and/or test arrangements in accordance with one or moreembodiments described herein may be able to detect defective cellshaving one or more cell defects, such as e.g. cell defects 901, 902,and/or 903 (or other defects), such that devices having defective cellsmay, for example, be filtered out.

In one or more embodiments, detection of defective cells may be carriedout by applying one or more test potentials to the device cells 120, orto one or more electrodes or electrode regions of the cells 120, forexample to carry out breakdown voltage measurements and/or dielectriclayer stress tests, etc.

For example, in one or more embodiments, testing may include or beachieved by varying a bias potential at the at least one additionalelectrode 111 of semiconductor device 900 between a first value (e.g. 0V) and a second value (e.g. some predeterminable upper limit), e.g.increasing the bias potential from the first value to the second value,and carrying out a low-current breakdown voltage measurement for each ofthe applied bias potentials. A deviation of the measured breakdownvoltage from a nominal or desired value at some value of the biaspotential may then, for example, indicate that semiconductor device 900may have one or more defective cells.

For example, in accordance with one or more embodiments, an electricalscan curve may illustratively be pushed through the cell(s) 120 todetect anomalies (defects) 901, 902, 903 in semiconductor device 900, asillustrated in FIG. 9.

FIG. 9 shows (in the left half of the figure) the electricalpush-through (indicated by arrows 920) of the scan curve for the case ofadditional electrode(s) 111 (e.g. Poly-S electrode(s)) being at a firstbias potential, e.g. 0 V, (represented by first potential curve 910 a inthe trench bottom area) and the case of electrode(s) 111 being at asecond bias potential, e.g. +12 V, (represented by second potentialcurve 910 b in the inter-electrode dielectric layer (e.g. POLOX) area).Illustratively, curves 910 a and 910 b may represent electricalpotential lines in semiconductor device 900 for two different values ofthe bias potential at the electrode(s) 111 (i.e., 0 V and +12 V) and agiven value of the potential at the first terminal electrode regions(e.g. 0 V) and a given value of the potential at the second terminalelectrode region (e.g. +30 V or +40 V). The electrical scan curve may bepushed from bottom to top into the cell(s) 120 according to the biasvoltage applied to additional electrode(s) 111 (e.g. Poly-Selectrode(s)). Anomalies (defects) 901, 902, 903 in the various cells120 of semiconductor device 900 may be detected at low current densitiesas they may cause a different shape of the potential curve and thus adifferent value of the breakdown voltage Ubr. In one or moreembodiments, a dynamical PAT evaluation algorithm may be applied to theUbr distribution and may filter out anomalous (defective) devices (e.g.chips).

FIG. 10 shows a cross-sectional view of another exemplary semiconductordevice 1000 for use with one or more embodiments.

Semiconductor device 1000 may be to some degree similar to semiconductordevice 100 described above. In particular, reference numerals which arethe same as there may denote the same or similar elements, which willthus not be described in detail again here.

Semiconductor device 1000 differs from semiconductor device 100 in thatsemiconductor device 1000 is configured as a diode. First terminalelectrode regions 102 may be of the same conductivity type as bodyregions 108 and may be of the opposite conductivity type as secondterminal electrode region 103. For example, first terminal electroderegions 102 may be p-doped (e.g. p+ doped) while second terminalelectrode region 103 may be n-doped, including for example highlyn-doped (e.g. n+ doped) first subregion 103 a and lightly n-doped (e.g.n− doped) second subregion 103 b. It may be understood that theconductivity type of all doped regions may be reversed. First terminalelectrode regions 102 may be anode regions and first terminal electrode104 may be an anode of the diode, while second terminal electrode region103 may be a cathode region and second terminal electrode 105 may be acathode of the diode, or vice versa.

Each device cell 120 of semiconductor device 1000 may include at leastone trench 130. An electrode 1011 may be disposed in the trench 130 andmay be electrically insulated from the semiconductor body 101 by meansof an electrically insulating layer 1012 that may surround the electrode1011. The electrodes 1011 may extend along body regions 108 and along atleast part of the second terminal electrode region 103 (e.g., at leastpart of the second subregion 103 b of the second terminal electroderegion 103, as shown). The electrodes 1011 may be electrically connectedto one another. The electrodes 1011 may contain or consist of anelectrically conductive material such as, for example, polysilicon or ametal or metal alloy, but other electrically conductive materials may beused as well. The electrically insulating layer 1012 may contain orconsist of an electrically insulating material such as, for example, anoxide, but other electrically insulating materials may be used as well.

FIG. 11 shows a test method 1100 according to various embodiments.

In 1102, a semiconductor device to be tested may be provided. Thesemiconductor device may be configured as a diode. The semiconductordevice may include at least one device cell. The at least one devicecell may include at least one trench, at least one first terminalelectrode region and at least one second terminal electrode region, andat least one electrode disposed at least partially in the at least onetrench. An electrical potential of the at least one electrode may becontrolled separately from electrical potentials of the at least onefirst terminal electrode region and the at least one second terminalelectrode region. For example, the at least one electrode may beelectrically disconnected or insulated from the at least one firstterminal electrode region and the at least one second terminal electroderegion.

In 1104, at least one electrical test potential may be applied to atleast the at least one electrode to detect defects in the at least onedevice cell.

In one or more embodiments, the semiconductor device may further includeor be configured in accordance with one or more features describedherein above in connection with semiconductor device 1000.

In one or more embodiments, the semiconductor device configured as adiode may be subjected to one or more of the test methods or testsdescribed herein above to detect defects in the at least one devicecell, for example a defect density scan, a reliability scan, anelectrode insulating layer stress test, a breakdown voltage measurement,and/or an avalanche test, by applying at least one electrical testpotential to at least the at least one electrode in a similar manner asdescribed herein above. To this end, it may be provided that the atleast one electrode disposed in the at least one trench may beelectrically disconnected from the first and second terminal electroderegions and may, for example, be coupled to a separate pad, as describedherein above. In one or more embodiments, the separate pad may later(e.g. after the test or tests have been carried out) be coupled toanother pad carrying a desired potential during normal operation of thesemiconductor device, as described herein above.

Illustratively, the semiconductor device configured as a diode andhaving at least one electrode disposed in a trench may be subjected tothe same or similar tests as the semiconductor devices described hereinhaving at least one gate electrode and having at least one additionalelectrode disposed in a trench. For example, a test arrangement inaccordance with one or more embodiments, including the semiconductordevice to be tested (i.e. the diode in this case) and the test device(e.g. test circuit or test equipment), may be configured in the same ora similar manner as the test arrangement 800′ described herein above inconnection with FIG. 8, except that the gate electrode 109 andconsequently the electrical connection 853 are missing.

A test method in accordance with various embodiments may include:providing a semiconductor device to be tested, the semiconductor deviceincluding at least one device cell, the at least one device cellincluding at least one trench, at least one first terminal electroderegion and at least one second terminal electrode region, at least onegate electrode, and at least one additional electrode disposed at leastpartially in the at least one trench, wherein an electrical potential ofthe at least one additional electrode may be controlled separately fromelectrical potentials of the at least one first terminal electroderegion, the at least one second terminal electrode region and the atleast one gate electrode; and applying at least one electrical testpotential to at least the at least one additional electrode to detectdefects in the at least one device cell.

In one or more embodiments, the semiconductor device may have a surfacearea (e.g. chip area) of greater than or equal to about 1 mm², forexample greater than or equal to about 2 mm², for example greater thanor equal to about 5 mm², for example greater than or equal to about 10mm², for example greater than or equal to about 20 mm².

In one or more embodiments, the semiconductor device may be configuredas a transistor.

In one or more embodiments, the at least one gate electrode may bedisposed at least partially in the at least one trench.

In one or more embodiments, the at least one additional electrode may beconfigured as a shield electrode.

In one or more embodiments, the at least one test potential may beconfigured to detect one or more defects in the at least one trench.

In one or more embodiments, the at least one cell may include at leastone contact trench, and the at least one test potential may beconfigured to detect one or more defects in the at least one contacttrench.

In one or more embodiments, the at least one test potential may beconfigured to determine a breakdown voltage of the semiconductor device.

In one or more embodiments, applying at least one test potential to atleast the at least one additional electrode may include forcing apredeterminable electrical current through the semiconductor device(e.g. transistor). The electrical current may have a constant orsubstantially constant current density. For example, the current densityof the electrical current may be held constant or substantially constantfor a predeterminable time period.

In one or more embodiments, the current density may be greater than orequal to about 0.5 A/mm² (amps per mm² of active device area, forexample greater than or equal to about 10 A/mm², for example greaterthan or equal to about 50 A/mm², for example greater than or equal toabout 100 A/mm² In one or more embodiments, the current density may benear a destruction limit of the device (e.g. transistor).

In one or more embodiments, applying at least one test potential to atleast the at least one additional electrode may include carrying out anavalanche test.

In one or more embodiments, the avalanche test may include applying oneor more avalanche pulses to the semiconductor device. In other words,the avalanche test may be a pulsed avalanche test.

In one or more embodiments, applying at least one test potential to atleast the at least one additional electrode may include applying aplurality of test potentials to the at least one additional electrode,and the method may further include measuring a breakdown voltage of thesemiconductor device for each of the plurality of test potentials.

In one or more embodiments, the at least one test potential may beconfigured to determine a strength of an insulating layer in the atleast one trench.

In one or more embodiments, the at least one additional electrode may beinsulated by an insulating layer disposed in the at least one trench,wherein applying at least one test potential to at least the at leastone additional electrode may include applying a plurality of testpotentials to the at least one additional electrode, and wherein themethod may further include: measuring a tunnel current through theinsulating layer for each of the plurality of test potentials.

In one or more embodiments, at least one of the at least one gateelectrode and the at least one additional electrode may includepolysilicon.

In one or more embodiments, the semiconductor device may include aplurality of device cells electrically connected in parallel, eachdevice cell including at least one trench, at least one first terminalelectrode region and at least one second terminal electrode region, atleast one gate electrode, and at least one additional electrode disposedat least partially in the at least one trench, wherein an electricalpotential of the at least one additional electrode may be controlledseparately from electrical potentials of the at least one first terminalelectrode region, the at least one second terminal electrode region andthe at least one gate electrode, wherein the at least one test potentialmay be applied to all device cells of the plurality of device cellssimultaneously.

In one or more embodiments, applying the at least one test potential mayinclude subjecting the semiconductor device to at least one of a defectdensity scan and a reliability scan.

In one or more embodiments, the method may further include analyzingtest results obtained by applying the at least one test potential, bymeans of dynamical part average testing (PAT).

In one or more embodiments, the semiconductor device may be formed in asemiconductor workpiece, the workpiece including a plurality of padsincluding at least a first pad coupled to the at least one firstterminal electrode region, a second pad coupled to the at least onesecond terminal electrode region, a third pad coupled to the at leastone gate electrode and a fourth pad coupled to the at least oneadditional electrode, wherein the fourth pad coupled to the at least oneadditional electrode may be electrically insulated from the first tothird pads.

In one or more embodiments, the method may further include: electricallyconnecting the fourth pad to at least one of the first to third padsafter applying the at least one test potential to at least the at leastone additional electrode.

In one or more embodiments, electrically connecting the fourth pad to atleast one of the first to third pads may be carried out in a back endprocessing stage of the semiconductor device.

In one or more embodiments, applying the at least one test potential toat least the at least one additional electrode may include using aplurality of probes.

In one or more embodiments, applying the at least one test potential toat least the at least one additional electrode may be carried out in afront end processing stage of the semiconductor device.

A test method in accordance with various embodiments may include:providing a workpiece, the workpiece including a transistor to betested, the transistor including a plurality of cells electricallyconnected in parallel, each cell including at least one trench, at leastone first terminal electrode region and at least one second terminalelectrode region, at least one gate electrode, and at least oneadditional electrode disposed at least partially in the at least onetrench, wherein an electrical potential of the at least one additionalelectrode may be controlled separately from electrical potentials of theat least one first terminal electrode region, the at least one secondterminal electrode region and the at least one gate electrode; andapplying a plurality of test potentials to at least the at least oneadditional electrode of the cells to detect defective cells among theplurality of cells.

In one or more embodiments, applying the plurality of test potentials toat least the at least one additional electrode of the cells may includeapplying a plurality of different bias potentials to the at least oneadditional electrode, wherein the method may further include measuring abreakdown voltage of the transistor for each of the bias potentials.

In one or more embodiments, the at least one additional electrode may beinsulated by an insulating layer disposed in the respective trench,wherein applying the plurality of test potentials to at least the atleast one additional electrode may include applying a plurality of testpotentials to the at least one additional electrode, and wherein themethod may further include measuring a tunnel current through theinsulating layer for each of the plurality of test potentials.

In one or more embodiments, the workpiece may further include aplurality of pads including at least a first pad coupled to the at leastone first terminal electrode region, a second pad coupled to the atleast one second terminal electrode region, a third pad coupled to theat least one gate electrode and a fourth pad coupled to the at least oneadditional electrode of each cell, wherein the fourth pad coupled to theat least one additional electrode may be electrically insulated from thefirst to third pads.

In one or more embodiments, applying the plurality of test potentials toat least the at least one additional electrode of the cells may becarried out in a front end processing stage of the workpiece; and themethod may further include electrically connecting the fourth pad to atleast one of the first to third pads in a back end processing stage ofthe workpiece.

A test arrangement in accordance with various embodiments may include: asemiconductor device to be tested, the semiconductor device including atleast one device cell, the at least one device cell including at leastone trench, at least one first terminal electrode region, at least onesecond terminal electrode region, at least one gate electrode, and atleast one additional electrode disposed at least partially in the atleast one trench, wherein an electrical potential of the at least oneadditional electrode may be controlled separately from electricalpotentials of the at least one first terminal electrode region, the atleast one second terminal electrode region and the at least one gateelectrode; and a test device configured to apply at least one electricaltest potential to at least the at least one additional electrode todetect defects in the at least one device cell.

A test method in accordance with various embodiments may include:providing a semiconductor device to be tested, the semiconductor devicebeing configured as a diode and including at least one device cell, theat least one device cell including at least one trench, at least onefirst terminal electrode region, at least one second terminal electroderegion, and at least one electrode disposed at least partially in the atleast one trench, wherein an electrical potential of the at least oneelectrode may be controlled separately from electrical potentials of theat least one first terminal electrode region and the at least one secondterminal electrode region; and applying at least one electrical testpotential to at least the at least one electrode to detect defects inthe at least one device cell.

A test arrangement in accordance with various embodiments may include: asemiconductor device to be tested, the semiconductor device beingconfigured as a diode and including at least one device cell, the atleast one device cell including at least one trench, at least one firstterminal electrode region, at least one second terminal electroderegion, and at least one electrode disposed at least partially in the atleast one trench, wherein an electrical potential of the at least oneelectrode may be controlled separately from electrical potentials of theat least one first terminal electrode region and the at least one secondterminal electrode region; and a test device configured to apply atleast one electrical test potential to at least the at least oneelectrode to detect defects in the at least one device cell.

While various aspects of this disclosure have been particularly shownand described with reference to specific embodiments, it should beunderstood by those skilled in the art that various changes in form anddetail may be made therein without departing from the spirit and scopeof the disclosure as defined by the appended claims. The scope of thedisclosure is thus indicated by the appended claims and all changeswhich come within the meaning and range of equivalency of the claims aretherefore intended to be embraced.

What is claimed is:
 1. A test method, comprising: providing a workpiececomprising a transistor to be tested, the transistor comprising aplurality of cells electrically connected in parallel, each of theplurality of cells comprising at least one trench, at least one firstterminal electrode region and at least one second terminal electroderegion, at least one gate electrode, and at least one additionalelectrode disposed at least partially in the at least one trench,wherein an electrical potential of the at least one additional electrodeis separately controllable from electrical potentials of the at leastone first terminal electrode region, the at least one second terminalelectrode region and the at least one gate electrode; and applying aplurality of test potentials to at least one of the at least oneadditional electrodes of the plurality of cells to detect defectivecells among the plurality of cells.
 2. The method of claim 1, whereinapplying the plurality of test potentials comprises applying each of theplurality of test potentials commonly to a plurality of the at least oneadditional electrodes of the plurality of cells.
 3. The method of claim1, wherein applying the plurality of test potentials comprises applyinga plurality of different bias potentials, wherein the method furthercomprises measuring a breakdown voltage of the transistor for each ofthe bias potentials.
 4. The method of claim 1, wherein each of the atleast one additional electrodes of the plurality of cells is insulatedby an insulating layer disposed in the respective trench, wherein themethod further comprises: measuring a tunnel current through theinsulating layer for each of the plurality of test potentials.
 5. Themethod of claim 1, wherein the workpiece further comprises a pluralityof pads including at least a first pad coupled to the at least one firstterminal electrode region, a second pad coupled to the at least onesecond terminal electrode region, a third pad coupled to the at leastone gate electrode and a fourth pad coupled to the at least oneadditional electrode of each cell, wherein the fourth pad coupled to theat least one additional electrode is electrically insulated from thefirst to third pads.
 6. The method of claim 5, wherein applying theplurality of test potentials is carried out in a front end processingstage of the workpiece; and the method further comprising: electricallyconnecting the fourth pad to at least one of the first to third pads ina back end processing stage of the workpiece.
 7. The method of claim 1,wherein respectively for each of the plurality of cells, a potential ofthe at least one additional electrode is electrically insulated frompotentials of each of the at least one first terminal electrode region,the at least one second terminal electrode region, and the at least onegate electrode.
 8. The method of claim 1, wherein applying the pluralityof test potentials comprises carrying out an avalanche test.
 9. Themethod of claim 8, wherein the avalanche test comprises applying one ormore avalanche pulses to the transistor.
 10. The method of claim 1,wherein applying the plurality of test potentials comprises subjectingthe transistor to at least one of a defect density scan and areliability scan.
 11. The method of claim 1, further comprising:analyzing test results obtained by applying the plurality testpotentials by means of dynamical part average testing (PAT).
 12. Themethod of claim 1, wherein respectively for one or more of the pluralityof cells, the corresponding at least one gate electrode is at leastpartially in the at least one trench.
 13. The method of claim 1, whereinrespectively for one or more of the plurality of cells, thecorresponding at least one additional electrode is configured as ashield electrode.
 14. The method of claim 1, wherein applying theplurality of test potentials comprises forcing a predeterminableelectrical current through the transistor.
 15. The method of claim 1,wherein respectively for one or more of the plurality of cells, at leastone of the corresponding at least one gate electrode and thecorresponding at least one additional electrode comprises polysilicon.16. A test method, comprising: providing a semiconductor device to betested, the semiconductor device being configured as a diode andcomprising at least one device cell, the at least one device cellcomprising at least one trench, at least one first terminal electroderegion, at least one second terminal electrode region, and at least oneelectrode disposed at least partially in the at least one trench,wherein an electrical potential of the at least one electrode isseparately controllable from electrical potentials of the at least onefirst terminal electrode region and the at least one second terminalelectrode region; and applying at least one electrical test potential toat least the at least one electrode to detect defects in the at leastone device cell.
 17. The method of claim 16, wherein respectively foreach of the at least one device cell, a potential of the at least oneadditional electrode is electrically insulated from potentials of eachof the at least one first terminal electrode region, the at least onesecond terminal electrode region, and the at least one gate electrode.